A restaurant group that operates multiple popular bars and eateries in Boston is alerting its customers to a credit card security breach that impacted its establishments earlier this year.

The Briar Group recently said that it became aware that its system was infiltrated sometime in October to early November, the group said on itssite. Restaurants and bars in the chain include the Harp, Gather, City Table, City Bar, Solas, Ned Devine's and Anthem Kitchen and Bar.

The Briar Group said that its investigation is "active and ongoing" and that it is working to determine the exact dates of the card data breach.

"We urge all of our customers during this period to monitor your credit card statements carefully for fraudulent charges," the group said in a statement on its website. "We want to assure you that the Briar Group takes the security of the personal information and bank data of all of our customers seriously. For the past several years, we have been working with data service and security professionals McGladrey to assure that we meet or exceed industry standards in terms of data security."

The group also said that since it became aware of the breach it has taken steps to address it and it is now confident that they system is secure and credit cards are safe to use at its establishments.

Those who notice unauthorized use on their card should contact their card issuer.